Business leaders vowed yesterday to fight a federal government plan to shoulder the plight of Americans who suffer repetitive-motion injuries working on computers and on assembly lines.

The Labor Department has proposed regulations calling for employers to fix conditions that require repetitive motion, overexertion or awkward posture.

“If OSHA persists in pushing forward this ill-considered regulation, then we will meet them in court,” said Randal Johnson, the U.S. Chamber of Commerce’s vice president for labor policy.

The proposal would cost employers an estimated $4.2 billion a year to redesign job sites and pay recovering workers.

“We are compelled to act. Employees are getting hurt,” said Charles Jeffress, assistant secretary for the Labor Department’s Occupational Safety and Health Administration.

Every year, 1.8 million workers suffer ergonomically related injuries — including carpal tunnel syndrome, tendinitis and back pain– and 600,000 miss work because of them, OSHA says.

The proposed rules cover 27 million Americans who work a wide range of jobs, from nurses’ aides who lift heavy patients, to airport baggage handlers and people who work at computers or on assembly lines.

Corporate groups argue that it’s hard to prove that supposed ergonomically based injuries are strictly work-related.

Under the regulations, someone with an ergonomic injury diagnosed by a doctor would be entitled to have the workplace problem fixed — for example, changing the height of a computer keyboard.

A worker who must have lighter duties while getting better would get normal pay and benefits, and someone who cannot work at all would be guaranteed 90 percent pay — and full benefits during recovery.

There will be public hearings on the proposed rules, which could not become final until next year at the earliest.